1. Field of the Invention
The present invention relates to a light emitting device and a method for manufacturing the same.
2. Description of the Background Art
In recent years, LEDs have come to be used frequently as light sources for illumination apparatuses. Methods for obtaining white light in the illumination apparatus using LEDs include, for example, a method using three kinds of LEDs, that is, a red LED, a blue LED, and a green LED, and a method utilizing a fluorescent material that converts excited light from a blue LED to emit yellow light. With respect to the light sources for illumination apparatuses, since white light having sufficient luminance is required, illumination apparatuses using a plurality of LED chips have been commercialized.
For one example of such an illumination apparatus, Japanese Patent Laying-Open No. 2001-007405 (Patent Document 1) discloses a light emitting diode 201 as schematically shown in FIG. 28. Light emitting diode 201 in the example shown in FIG. 28 has a structure in which on a glass epoxy substrate 202 having a cathode electrode 203 and an anode electrode 204, the back face of a light emitting diode element 205 is secured, with a fluorescent material containing layer 206, formed by dispersing a fluorescent material in an adhesive agent, being interposed therebetween. Moreover, in light emitting diode 201 in the example of FIG. 28, light emitting diode element 205 is sealed by a resin sealing member 207 on its upper face side, and an auxiliary fluorescent material containing layer 208 is formed on the upper face of resin sealing member 207. Patent Document 1 describes that by providing this structure, the light emission luminance of the white light emitting diode can be improved, and that shifts in chromaticity can be suppressed.
However, in light emitting diode 201 shown in FIG. 28, since light emitting diode element 205 is secured on glass epoxy substrate 202 with fluorescent material containing layer 206 interposed therebetween, heat generated in light emitting diode element 205 is directly released to the fluorescent material in fluorescent material containing layer 206 to presumably cause the problem that the fluorescent material is altered.
Moreover, for example, Japanese Patent Laying-Open No. 2004-071726 (Patent Document 2) discloses a light emitting device 301 as schematically shown in FIG. 29. A light emitting device 301 in the example of FIG. 29 includes a package 302 having a first concave section 303 and a second concave section 304 including this first concave section 303 (first concave section 303 is formed in second concave section 304). A LED chip 305 capable of emitting light within a blue color range is mounted in first concave section 303, and first concave section 303 is filled in such a manner as to cover this LED chip 305 so that a first fluorescent layer 306 is formed. Moreover, a LED chip 307 capable of emitting light within a blue color range is mounted in second concave section 304, and second concave section 304 is filled in such a manner as to cover this LED chip 307 and first fluorescent material layer 306 so that a second fluorescent material layer 308 is formed. Moreover, in light emitting device 301 in the example of FIG. 29, the positive electrode and the negative electrode of a lead electrode 309 are integrally formed in package 302, and the n-type electrode and p-type electrode of each of LED chips 305 and 307 are electrically connected to the positive pole and the negative pole of this lead electrode 309 by using conductive wires 310. Patent Document 2 describes that by providing this structure, it is possible to provide a light emitting device that can restrain occurrence of chromaticity shifts due to a change in ambient temperature.
Light emitting device 301 shown in FIG. 29, however, has a complicated structure in which two concave sections (first concave section 303 and second concave section 304) are formed in package 302 and two LED chips 305 and 307 are mounted, with two kinds of fluorescent material layers (first fluorescent material layer 306 and second fluorescent material layer 308) having different materials being provided therein; therefore, in manufacturing such light emitting device 301, complicated processes are required and the manufacturing cost is high.